1. Field of the Invention
The invention relates to a scanner capable of positioning a scan start position and related method, and more particularly, to a scanner capable of using an arc calibration patter for positioning a scan start position and related method thereof.
2. Description of the Prior Art
Over the last decade, the development of computer peripherals and other electronic apparatus has progressed almost daily. These devices are now utilized universally in daily life. Take the scanner as an example. A scanner is a very popular electronic apparatus for scanning a document and generating corresponding data, or for converting image data, such as photographs, into a digital format that can be operated on and modified with a computer. In addition, the scanner may provide some additional functions such as facsimileing image data through a telephone line, sending image data by e-mail through the Internet, copying image data as a copy machine, or even posting converted image data on the Internet.
Referring to FIGS. 1-2, FIG. 1 illustrates a perspective view of a scanner 10 according to the prior art and FIG. 2 is a block diagram illustrating the functionality of the scanner 10. The scanner 10 includes a housing 12, a transparent platen 14, an optical engine 16, a motor 18, and a control module 20. The transparent platen 14 is disposed on the housing 12 for supporting a document 22. The motor is electrically connected to the control module 20 and the optical engine 16. The control module 20 is used to control the motor 18 for moving the optical engine 16 according to a first direction. Preferably, the optical engine 16 is driven in a stepping manner to scan the document 22 and generate image signals corresponding to the document 22. The motor 18 can be a stepping motor, a servomotor, or a DC motor.
Typically, the optical engine 16 is returned to a home position after scanning the document 22 and before the next scan is conducted, the optical engine 16 must be precisely moved from the home position to a scan start position. By precisely moving the optical engine 16 to the scan start position, the user could prevent unwanted portion of the documents from being scanned and that the optical engine 16 could scan all of the required documents, thereby increasing the quality of the scan. The conventional method of scanning documents typically involves forming a reference pattern in the scanner 10 before the scanner 10 and presetting the location of the reference pattern and the scan start position. After the optical engine 16 scans the reference pattern, the control module 20 would control the motor 18 to drive the optical engine 16 to move a few more steps to reach the scan start position and start scanning the documents 22. For instance, U.S. Pat. No. 5,144,455 discloses a means of utilizing a black block as a reference pattern, in which an optical engine would have to move step by step to scan all the lines of the black block for defining a scan start position. The drawback of this method is that a significant amount of time is spent on detecting the scan start position. For instance, if a resolution of 600 dpi is used to scan a block having a width of 2 mm, it would take the motor 18 to drive the optical engine 16 for 47 steps before defining a scan start position.
Taiwan Patent No. 462179 discloses another means of utilizing an isosceles right-angled triangle as a reference pattern. In this example, an optical engine would scan a distance between a side (such as the side adjacent to the 90 degree angle of the isosceles right-angled triangle) and two coordinates on the two other sides of the triangle to determine the scan start position. The drawback of this invention is that if an error occurs during the printing of the reference pattern of the isosceles triangle onto the housing or during the installation of the calibration sheet of the reference pattern, the setting for the isosceles triangle would be incorrect and the distance scanned by the optical engine between the side of the triangle and the two coordinates on other sides would not be the actual distance. As a result, the scan start position could not be positioned accurately. Hence, how to improve the accuracy of the current method for positioning the scan start position for an image scanning device has become a critical task.